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        <td class="header">&nbsp; Snaphu Unwrapping</td>
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<h3>Unwrapping with SNAPHU</h3>After creating a wrapped interferogram stack, use the SNAPHU Export to prepare the data for unwrapping with SNAPHU.<br>
<br>


<p>
    The main purpose of SNAPHU data export functionality is three-fold:
</p><ol>
    <li>
        To export data (bands) in the format compatible for SNAPHU processing,
    </li>
    <li>
        To build a SNAPHU configuration file (snaphu.conf), the file where processing parameters for SNAPHU are
        being stored,
    </li>
    <li>
        To construct a <i>container</i> product that will store metadata and bands to be used when SNAPHU results
        are being ingested back into the Toolbox.
    </li>
</ol>Next, run SNAPHU-Unwrapping.<br>
<br>
If SNAPHU hasn't been installed, SNAP will download and install the
software on Linux and Windows. You can also download and install it
yourself from <a href="http://step.esa.int/main/third-party-plugins-2/snaphu/">http://step.esa.int/main/third-party-plugins-2/snaphu/</a><br>
<br>
Select you input product and output folder and press Run to execute the SNAPHU command.<br>
<br>
<span style="color: black; font-family: Verdana,sans-serif; font-size: 12px; font-style: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; background-color: rgb(255, 255, 255); display: inline ! important; float: none;">After
the phase is unwrapped it can be imported to SNAP for further analysis
using Radar-&gt;Interferometric-&gt;Unwrapping-&gt; SNAPHU Import.</span><br>
<h4>About SNAPHU<br>
<em></em></h4>
<p style="color: black;"><span style="font-family: Verdana,sans-serif; font-size: 12px; font-style: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; background-color: rgb(255, 255, 255); display: inline ! important; float: none;">Two-dimensional
phase unwrapping is the process of recovering unambiguous phase data
from a 2-D array of phase values known only modulo 2pi rad. SNAPHU is
an implementation of the Statistical-cost, Network-flow Algorithm for
Phase Unwrapping proposed by Chen and Zebker. This algorithm poses
phase unwrapping as a maximum a posteriori probability (MAP) estimation
problem, the objective of which is to compute the most likely unwrapped
solution given the observable input data. Because the statistics
relating the input data to the solution depend on the measured
quantity, SNAPHU incorporates three built-in statistical models, for
topography data, deformation data, and smooth generic data. The posed
optimization problem is solved approximately with use of network-flow
techniques. As SNAPHU uses an iterative optimization procedure, its
execution time depends on the difficulty of the interferogram</span>
</p>



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